微波、冷冻预处理对改善尾巨桉木材干燥性能的影响

Improving the dry-ability of Eucalyptus by pre-microwave or pre-freezing treatment

桉树木材在干燥过程中常伴有开裂和皱缩等严重的干燥缺陷,为了减少桉树皱缩等干燥缺陷,提高桉树的干燥质量和探讨皱缩的形成原因,采用冷冻处理和微波辐射两种方法对尾巨桉木材进行预处理,研究微波、冷冻处理后尾巨桉木材的渗透性、干燥速度和木材的皱缩特性。结果表明:两种方法均能不同程度改善木材的渗透性,提高木材的干燥速度,减少木材的皱缩。对照材和微波辐射材,皱缩均发生在心、边材的交接处,部分木纤维扭曲,相互挤压,细胞腔变得狭小,形成扭曲带,相邻扭曲带的木纤维向相反方向挤压、溃陷;前者扭曲带宽可达5～20个细胞,皱缩深度为0.76 mm,后者扭曲带为5～10个细胞,皱缩深度为0.35 mm;冷冻预处理材表面未见明显皱缩痕迹,细胞皱缩程度不明显,扭曲带(1～2个细胞宽)隐约可见。

The drying defects,such as splits,checks and collapses,are developed during the drying of Eucalyptus urophylla×E.grandis.In order to improve the dried wood quality by reducing those drying defects,the reasons that caused the collapse was explored.The effect of two pre-treatments,i.e.,microwave and freezing,on wood permeability,drying rate and characteristics of collapse,were investigated.The results indicated that the permeability was more or less increased,the drying rate was raised and the collapse was reduced by using these treatments.On the control and microwave treated wood,it was observed that the crumples or wrinkles took place on borders of heartwood and sapwood.It was also seen that some wood fibers were twisted and squashed each other,their pit chambers were narrowed and the twist bands which vicinity squashed and collapsed in opposite directions were formed.The width of the twist band included 5—20 cells and the depth of the collapse was 0.76 mm on the control wood.While the width of the twist band included 5—10 cells and the depth of the collapse was 0.35 mm on the microwave treated wood.No considerable collapses were found and twist bands with a width of 1—2 cells were observed vaguely on the freezing treated wood.